A known light source unit for a vehicle is arranged above an armrest and configure to illuminate the armrest. With the illumination, the visibility of switches on the armrest improves.
In such a configuration, light emitted from a light source toward the armrest may be reflected by the upper surface of the armrest and directed to eyes of an occupant. As a result, the occupant may be dazzled by the reflected light. Furthermore, because of the reflected light, a mirror image of the light source may appear on the upper surface of the armrest. This may decrease the decent appearance. Upper surfaces of many armrests are polished to provide decent appearances, that is, the upper surfaces have high light reflectivities. Therefore, the above problems are more likely to occur.
An illumination device or a light source unit arranged in an interior part, such as a door trims, needs to be configured to direct light emitted from the light source toward a specific direction so that the light does not travel toward eyes of an occupant.